Nowadays, magnetic elements such as inductors and transformers are widely used in power supply apparatuses or other electronic devices in order to generate induced magnetic fluxes.
Take an inductor as an example. FIG. 1A is a schematic exploded view illustrating an inductor with an air gap. FIG. 1B is a schematic assembled view illustrating a portion of the inductor of FIG. 1A, in which the bobbin and the winding coil are not shown. The inductor 1 may be applied to a power factor correction circuit or a resonant circuit of a power supply apparatus. The conventional inductor 1 comprises a bobbin 10, a first magnetic core 11, a second magnetic core 12, and a winding coil 13. The bobbin 10 comprises a channel 101 and a winding section 102. A middle post 111 of the first magnetic core 11 and a middle post 121 of the second magnetic core 12 are embedded within the channel 101. The winding coil 13 is wound around the winding section 102. The first magnetic core 11 and second magnetic core 12 are arranged on opposite sides of the bobbin 10. Moreover, an air gap 14 is formed between a middle post 111 of the first magnetic core 11 and a middle post 121 of the second magnetic core 12. After the bobbin 10, the first magnetic core 11, the second magnetic core 12 and the winding coil 13 are combined together, the inductor 1 with the air gap 14 is fabricated.
Recently, the magnetic element of the power supply apparatus is designed to have increased power (watt), reduced height and increased winding space. In the inductor 1, the winding coil 13 is fixed on the bobbin 10 and arranged between the first magnetic core 11 and second magnetic core 12, and the air gap 14 is covered by the winding coil 13. Due to the volume of the bobbin 10, the space between the first magnetic core 11 and second magnetic core 12 for accommodating the winding coil 13 is restricted and the coil utilization is reduced. Under this circumstance, since the diameter of the winding coil 13 is limited, the overall temperature of the inductor 1 is very high and the working efficiency of the inductor 1 is impaired. Moreover, the single air gap 14 between the middle post 111 of the first magnetic core 11 and the middle post 121 of the second magnetic core 12 may avoid the generation of magnetic saturation. However, the larger air gap may result in higher leakage flux. Under this circumstance, the eddy loss is increased, the overall temperature of the inductor 1 is increased, and the working efficiency of the inductor 1 is reduced.
Therefore, there is a need of providing a magnetic element with multiple air gaps in order to eliminate the above drawbacks.